Pipes used for a boiler and a turbine, which are provided to a thermal power plant and a factory, are exposed to a high-temperature environment. Thus, creep deformation, in which distortion becomes greater from a weld as the center, is easily caused as time passes. Therefore, such distortion in the pipes is regularly inspected, to predict the residual life of the pipes (see Patent Literature 1).
A method of inspecting such a pipe for distortion includes forming a metal thin film on a surface of the pipe in advance, and performing image analysis of the surface of the metal thin film as to its unevenness.